server.js

const express = require('express');
const mongoose = require('mongoose');
const bodyParser = require('body-parser');
const passport = require('passport');
const bearerToken = require('express-bearer-token');
const jwt = require('jsonwebtoken');

// load the config file if no database unique resource identifier is present
if (!process.env.DB_URI){ require('./config/env.js'); }

// set port to the environment variable settings or 3000 if none exist
const port = process.env.PORT || 3000; 

// connect to db using environment variables
const databaseConnectionString = 'mongodb://' + process.env.DB_USERNAME + ':' + process.env.DB_PASSWORD + '@' + process.env.DB_URI;
mongoose.Promise = global.Promise;
mongoose.connect(databaseConnectionString);

// instantiate express app
const app = express();

// middleware that accepts urlencoded form data
// https://github.com/expressjs/body-parser#bodyparserurlencodedoptions
app.use(bodyParser.urlencoded({ extended: true }));

// middleware that accepts json 
// https://github.com/expressjs/body-parser#bodyparserjsonoptions
app.use(bodyParser.json());

// extracts bearer token from request
// https://github.com/tkellen/js-express-bearer-token
app.use(bearerToken());

// instantiate passport
app.use(passport.initialize());

// set passport login and signup strategies
const localSignupStrategy = require('./passport/local-signup');
const localLoginStrategy = require('./passport/local-login');
passport.use('local-signup', localSignupStrategy);
passport.use('local-login', localLoginStrategy);

// set cross origin resource sharing (CORS) policy
app.use((req, res, next) => {
	res.header('Access-Control-Allow-Origin', '*');
	res.header('Access-Control-Allow-Credentials', 'true');
	res.header('Access-Control-Allow-Methods', 'GET, HEAD, OPTIONS, POST, PUT, DELETE');
	res.header('Access-Control-Allow-Headers', 'Access-Control-Allow-Headers, Authorization, Origin, Accept, X-Requested-With, Content-Type, X-Access-Token');
	res.header('Cache-Control', 'no-cache');
	next();
});

// static info routes
require('./routes/static.js')(app);

// authentication routes
require('./routes/auth.js')(app, passport);

// api routes
require('./routes/api.js')(app);

// launch server
app.listen(port, () => {
	console.log(`API running on port ${port}`);
});